Variable geometry ducts are widely used, for example, in conjunction with turbo engine inlets and nozzles; and in conjunction with variable geometry wind tunnel walls and inlets; and also as inlet ducts, combustor and nozzle walls in variable geometry ram jet engines. Examples of such variable geometry ducts are disclosed, for example, in U.S. Pat. Nos. 3,265,332; 3,589,379 and 4,620,679. Variable geometry ducts in the prior art, as shown in the patents listed above, are usually formed by a series of side-wall panels which are controlled by appropriate actuators to move in and out as a function of the amount of gas carried by the duct in response to the demands of the engine, or other instrumentality fed by the ducts.
It is also the practice in the prior art to pressurize the cavity behind the moveable duct panels to equalize the pressure in the cavity with the fluid pressure in the duct. This equalization of pressures on both sides of the moveable panels minimizes the actuation forces required to move the panels, and also minimizes leakage of combustible gas from the duct into the cavities behind the moveable panels.
Problems have arisen in the past in sealing such variable geometry ducts, and an objective of the present invention is to provide a solution to the problems.